1. Field of the Invention
The invention relates to the field of heat sealing caps to containers. In particular, the invention is an air cooled inductive sealing apparatus in which the power supply and electronics are enclosed so that the apparatus may be spray washed, in accordance with NEMA 4 standards.
2. Discussion of the Prior Art
For some time, the food industry has been hermetically sealing the openings of containers to retain freshness of food and to prevent contamination from microorganisms or other bacteria. Similarly, drug manufacturers have been sealing bottles with seals that cannot be unnoticeably removed in an effort to prevent tampering with the contents. Beyond the food and drug industry, manufacturers of liquids or air sensitive products also tightly seal their product containers to prevent leakage and prolong shelf life.
One method to obtain such seals is inductive sealing. Inductive sealing requires an electromagnetic-field-producing apparatus and a foil-polymer seal. Typically, the apparatus includes at least one coil of wire wound to produce an electromagnetic field when electric current is supplied to the coil. It is well known in the art that electromagnetic fields induce eddy currents within metal which in turn heat the metal. The seal comprises a thin layer of aluminum foil onto which is laminated a polymer layer that is molecularly compatible with the container to be sealed. When the seal is placed onto the container and the container is placed within the electromagnetic field, the foil is heated which melts the layer of polymer. Removing the seal from the electromagnetic field allows the polymer to cool and molecularly fuse with the container to create an air-tight seal.
Industrial settings, the primary environment for induction sealers, typically have strict cleanliness requirements, particularly in the heavily regulated food and drug industries. To comply with these regulations, manufacturers are typically required to wash down the production area with water and/or a disinfectant. Thus, the power supply circuitry of induction sealers must be enclosed in accordance with the National Electrical Manufacturers Association (NEMA) standard 4, i.e., a completely sealed enclosure that is suitable for wash-down.
As is known by those skilled in the art, however, the strength of the electromagnetic field chiefly depends upon the number of turns in the wire coils and the amount of current supplied to the coils. To produce an electromagnetic field adequate for commercial inductive sealing, typically the power supply must output power in the order of a few kilowatts, which produces a great deal of heat. Thus, the power supply must be cooled in order to function properly.
Many methods of cooling are known in the art, in particular, it is known to vent and/or force air through the power supply. Venting the power supply cabinet in any way, however, precludes the sealing needed to maintain NEMA 4 standards. It is also known to remove heat by circulating cool water through pipes or tubes running through the enclosure containing the power supply. Water cooling, however, requires complicated piping configurations that increase the size and cost of the sealing apparatus. An air cooled inductive sealing apparatus is needed, therefore, that has a power supply and electronic circuitry enclosed in a NEMA 4 cabinet.